Synthetic lubricants



United States Patent SYNTHETIC LUBRICANTS Louis A. Mikeska and Paul V. Smith, Jr., Westfield, N. J., assignors-to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Original application August 3, 1948, Serial No. 42,333. Divided and this application "June 29, 1953, Serial No. 364,915

2 Claims. (Cl. 25246.6)

This invention relates to a new .class of compounds which have been found to be particularly suitable for use as synthetic lubricants because of their low pour point, high viscosity index and unusually good load carrying properties. These compounds have also been found to be usefulas addition agents for mineral lubricating oils, in which they serve as improvers of the load carrying properties of the same.

'In the lubricant art, considerable progress has been ,realized in recent years in the production of lubricants characterized by one or more specific properties and adapted for particular uses. In the main, this progress can be contributed to two developments: the first, new refining procedures, and the second, addition agents capable of imparting particular properties to available lubricants.

Thus, viscosity index improvers and pour depressants are added to automotive lubricants to render the lubricants more adaptable to wide changes in temperatureconditions, while other agents are added to improve the load carrying properties of a lubricant which is to be employed, for example, under extreme pressure conditions.

Recently, in an effort to obtain superior lubricants endowed with specific and superior characteristics, a new field has been explored, namely, the synthesis of lubricants from various materials. Esters represent one class of materials which have attracted unusual interest as synthetic lubricants. In general, they are characterized by higher viscosity indices and lower pour points than mineral oils of corresponding viscosity. The esters described in the present specification have been found to exhibit very low pour point, high viscosity indices, and in addition unusually good load carrying properties. Lubricants possessing such properties are of special value inthe lubrication of engines which are subjected to high temperatures such as combustion turbine engines, particularly those -of theprop-jet type. Mineral Oil lubricants containing added viscosity index improvers, thickenersorother-highly non-volatile additives are undesirable for use in such engines because of the tendency to leave a residue which would accumulate and interfere with the operation of the engine. A synthetic lubricant of the type described in the present specification is especially adapted to'use under such conditions, since the lubricant contains no additives and thus tends to leave no residue upon volatilization.

The new compounds of the present invention, adapted particularly for use as synthetic lubricants, comprise a new class of organo-substituted phosphoric acids, the class being defined by the general formula ORX1R1 oP-onxm,

in which R represents a saturated aliphatic hydrocarbon group of 2 to 3 carbon atoms; X1, X2, and X3 each represent oxygen or sulfur; and R1, R2, and R3 each represent an organic group which may be (1) an alkyl group, either straight chain or branched, containing 1 to 18 "2 carbon atoms, or (2) a series of saturated aliphatic hydrocarbon groups, straight chainor branched, interlinked by oxygen or sulfur atoms, the-total number of carbon, oxygen and sulfur atoms being from 4-to 18. The maximum number of oxygen or sulfuratoms or both in agiven radical R1, R2 or Rs is not greater than 5, and there is a chain of at least two carbon atoms between the atom X1, X2, or X3 and the first oxygen ,or sulfur atom in .such radical and a similar chain of at least'two carbon atoms between each other pair of oxygen or sulfur atoms in the radical; and the total number of carbon, oxygen and/or sulfur atoms in all of the radicals joined to OP of the formula .is about 24 to about 70. The more preferred compounds are those in which X1, X2, and Xarepresent the same oxygen or sulfur atom 'andRi, R2, and Rsrepresent the same organic radical. In such cases, when R1, R2, and R3 represent an alkylgroup, such group 'shouldcontain 4 to 18 carbon atoms.

The organo phosphateso-f the present-invention may be conveniently prepared by contacting about three molecular proportions of 'a suitable ether alcohol or thioether alcohol, or mixtures of such alcohols in amounts totalling three molecular proportions of alcohol, with one molecular prportion of phosphorus oxychloride in the presence of a suitable mediumsuch as benzene. When-phosphorus oxychloride is employed it may be desirable to have present a basic substance such as pyridine to absoil: the hydro-gen chloride produced in the reaction. A typical method suitable for preparing any of the compounds of the present invention will'be described in detail below. The ether alcohols and thioether alcohols may be prepared ingreat-var'iety by the well known method-of reacting alkylene oxides -with alcohols-or mercaptans. A class 'of ether alcohols which-are particularly suitable for the preparation of the new compounds of the present invention are the Carbitols, especially those whichhave the general formula where' R'is an alkyl group of 14 to 12 carbon atoms.

Among the ethenalcohols and thioether alcohols which vhave been found 'to be particularly suitable for use as starting materials in the formation of the organo phos- 'phates of the present invention may be mentioned the following, although -it is to be understood that these are ;illustrative.only and the invention is not to be considered lirnited to the-use of suchcompounds:

zEthylene glycol mono-methyl ether Ethyleneglycolmono-n-butyl ether Ethylene glycol mono-2-ethylbutyl ether Ethylene glycol mono-2-ethylhexylether Ethylene glycol mono tert-octy'l ether B-n-Butylmercaptoethanol fl-tert.-Octylmercaptoethanol B Dodecylmercaptoethanol Diethylene glycol mono-n butyl ether Diethylene.glycolmono-2-ethylbutylether Diethylene glycol mono-2-ethylhexyl ether Propylene glycol mono-n-butyl thioether Propylene glycol mono-tert.-octyl thioether Propylene glycol mono-n-dodecyl thioether n-Butylmercaptoethoxyethanol tert.-Octylmercaptoethoxyethanol n-Dodecylmercaptoethoxyethanol n-Butylmercaptopropoxypropanol tert.-Octylmercaptopropoxypropanol n-Dodecylmercaptopropoxypropanol Propyleneglycol mono-n-butyl ether Dipropylene glycol monomethyl ether Dipropylene glycol monoethyl ether Dipropylene glycol mono-n-butyl ether Tripropylene glycol monomethyl ether Tripropylene glycol monoethyl ether they are of particular interest as synthetic lubricants. In addition to the use of these materials alone as synthetic lubricants, they are valuable for improving the film strength and oiliness properties of mineral oils with which Tripropylene glycol mono-n-butyl ether 5 they are blended. For this purpose, they are preferably Propylene glycol monoisopropyl ether blended in proportions ranging from 1% to by Dipropylene glycol monoisopropyl ether weight of the mineral oil. The data in the last column Tripropylene glycol monoisopropyl ether of Table I show the usefulness of these compounds when Many of the above listed ether alcohols formed by the 10 blended w th a mineral 011. The unblende d mineral oil reaction of propylene oxide with aliphatic alcohols are employed In these tests was ciapable of y y only i known in the industry as Dowanols 7, Weights on the Almen machine under similar conditions When the esters of the present invention are emii 1 1 b n b t k hi h b ployed as lubricating oils, addition agents, such as thick- 3 3 nca.mg 0 i f i. g eners, pour depressants, detergents, antioxidants, dyes, 15 Improve In 0a 'carrymg capacity e a e etc., may be present if d i new compounds of the present invention may be derived I Data will be given below showing properties of four i theyfqnous types of crude pefmleuin and contypical examples of organo phosphates illustrating the g 2 1 .3 or ig of i l g present invention, these having been prepared by react- $528 6 y 6 2 5 me ing phosphorus oxychloride with butyl Carbitol, 2-ethylm so 6 use Sue S ose 0 y hexyl Cellosolve, a mixture of two-thirds mol of butyl the Po Ymematm of olefins Or.by the hydrogeniltlon of Carbitol and one-third mol of methyl Cellosolve, and F I products T base 0.11s may y conslderably B-tert.-octylmercaptoethanol, respectively. The properties i g gg g if i g g (iepgndmg upon the listed show the particular suitability of the products for p If i 5 i 22 3;; esue h thj k use as synthetic lubricants. The products were in each 25 eners Ourde i as case formed by conducting the reaction in the following dd p h f an an 10x1 6 may e manner: A mixture of one mol of the alcohol, 1.1 mols a e i g mineral 9 cmilpcsltm prepared m accordof pyridine, and 92 ml. of benzene was colled to 5 i t g i g C., and then 51.1 g. /3 mol) of POCla was dropped in at A Is g igz 0 enal Number 42333 filed such a rate that the temperature did not exceed 10 C. $2 i i andoned' When the addition was complete, the mixture was refluxed 1 A for two hours, after which 150 ml. of water was added in h 2 1:3; Composmon of matter the compound hav' and the benzene layer separated. The latter was washed g OP OCH2CH SC H several times with water until it was neutral. After 2 8 17 3 drying over a desiccant such as Drierite (an anhydrous P -Q a W group. c so th l t was di till d ff t 5 mm pressure 2. A mineral lubricating oil containing dissolved thereand a bath temperature of 200-225 C. In about 6% y Weight of h PO The four products produced by the above typical reaction method were found to have the properties set forth ,OHOCHzCHzSCaHHh in Table I. 40 where the group CaH1'z is a tert.-octyl group.

Table l ASTM Kinematic Viscosity gg g fffi P ASTM E Alcohol Reacted with P001; Slope v.1

100 F. 210 F. Alone Mfieral Butyl Oarbitol -35 13.029 3.392 0.701 154 '15 11 2-Ethyl1l31exy} gellgsollv 35 86. 700 12. 908 0. 595 134 15 15 $8% a gg i;: 36.660 7.322 0.617 152 B-tert.-Oety1mercaptoethanol 3689.0 146.9 15' 6 1 Diethylene glycol monobutyl ether.

2 Ethylene glycol mono-2-ethyl hexyl.

3 Ethylene glycol monomethyl ether.

conventionally refined coastal naphthenic oil of 42 seconds Saybolt mineral oil carried only three weights on the Almen machine.

The above data indicate that the materials tested possess an uncommonly low pour point, high viscosity index, and high-load carrying characteristics, and since these materials have a viscosity within the lubricating oil range viscosity at 210 F. The unblended References Cited in the file of this patent UNITED STATES PATENTS 2,372,244 Adams Mar. 27, 1945 

2. A MINERAL LUBRICATING OIL CONTAINING DISSOLVED THEREIN ABOUT 6% BY WEIGHT OF THE COMPOUND 